Report nested subscript arity errors at the right line in old parser - #22045
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The old parser pinned every type node to the outer annotation line, so arity errors in nested subscripts were reported at the wrong line. Use the subscript's own source line instead, matching the native parser. Type comments and string annotations keep the outer line, since their nodes only have fragment-relative positions. Fixes python#21480.
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According to mypy_primer, this change doesn't affect type check results on a corpus of open source code. ✅ |
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September 24, 2026 23:46
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Fixes #21480.
The old parser pinned every type node to the outer annotation line, so an arity error in a nested subscript was reported at the wrong line:
Old parser said line 1, native parser says line 3. Now both say line 3.
TypeConverter.visit_Subscriptuses the subscript's own source line for theUnboundType. Type comments and string annotations keep the old behavior through a newis_fragmentflag, since nodes parsed from those fragments only have fragment-relative line numbers.Added
testColumnNestedSubscriptArityErrorLine_old_parserto check-columns.test. It fails before the fix (error at the outer line) and passes after. Full testcheck/testparse/testsemanal run: 9030 passed.